(organic chemistry) The phenolic heterocycle 2,4-dihydroxypteridine that is related to riboflavin

(biochemistry) An enzyme, involved in riboflavin biosynthesis, that catalyzes the chemical reaction 1-deoxy-L-glycero-tetrulose 4-phosphate + 5-amino-6-(D-ribitylamino)uracil ⇌ 6,7-dimethyl-8-(D-ribityl)lumazine + 2 H₂O + phosphate.